against
prep.prep. in opposition to someone or something. You use this when you are competing with another person, or when you disagree with an idea. It can also mean touching something for support, like leaning on a wall.
prep. in opposition to, or in competition with, a person or entity; also indicates physical contact or pressure toward a surface. Functions as a head of a prepositional phrase, typically followed by a noun or pronoun object.
The local team plays against their rivals tomorrow.
The workers decided to protest against the new company policy because they felt it was unfair.
Leaning against the cold stone wall, the traveler watched the protesters march against the government's recent decision to increase taxes on imported goods.
Etymology tree ▲ Proto-Indo-European *h₁en- Proto-Indo-European *h₁en- Proto-Indo-European *h₁én Proto-Germanic *in Proto-Indo-European *ǵʰengʰ-der. Proto-Germanic *ganganąder.? Proto-Germanic *gagin Proto-Germanic *in gagin Proto-West Germanic *in gagin Old English onġēander. Middle English ayenes English against Formed from Middle English ayenes, agenes, againes (“in opposition to”), a southern variant of agen, or directly from again, either way with adverbial genitive singular ending -es; the parasitic -t was added circa 1350, probably by confusion with the superlative ending -est. By surface analysis, again + -st (excrescent ending). Cognate with Saterland Frisian juun (“against”), West Frisian tsjin (“against”), Dutch tegen (“against”), German Low German gegen (“against”), German gegen (“against”), Icelandic gegn (“against”).
Always followed by an object. When used to indicate physical contact, it implies pressure or support from the object.